Characterization of two Ni–Cr dental alloys and the influence of casting mode on mechanical properties

PurposeThe aim of this study was to evaluate the tensile strength, elongation, microhardness (MHV), composition and microstructure of two Ni–Cr based alloy, cast under different casting conditions.MethodsBefore casting, the alloy ingots were evaluated as regards composition (EDX) and microstructure (Optical microscopy, SEM and EDX). The casting conditions were as follows: electromagnetic induction in an environment controlled with argon (EWA), electromagnetic induction in an environment under vacuum (EWV), electromagnetic induction without atmosphere control (EWNC) and blowtorch (BT). For each condition, 16 specimens were obtained, each measuring 25 mm high and 2.5 mm in diameter. The ultimate tensile strength (UTS) and elongation (EL) tests were performed in a Kratos machine (1.0 mm/min). Fractured specimens were embedded in bakelite resin and polished for Vickers Microhardness analysis (1000 g/10 s) with 4 penetrations in each specimen. The UTS, EL and MHV results were evaluated for two-way ANOVA and Tukey's test (α = 0.05).ResultsThe cross-product interaction was statistically significant for all properties evaluated (p < 0.0001), lower UTS, VHN and higth elongation means were observed for the Ni–Cr–Mo–Be alloy tested when cast under the induction/argon (p < 0.05). Higher UTS means were found for Ni–Cr–Mo–Ti alloy tested when cast under the induction/vacuum, and induction/air and flame/air condition (p < 0.05). The two alloys show a microstructure with a dendritic formation with the presence of eutectic presence.ConclusionThe Ni–Cr–Mo–Ti alloy showed higth UTS, MHV and lowest EL comparaded with the tradicional Ni–Cr–Mo–Be, that show lowest UTS, MHV and higter EL when cast on induction/argon.     

Mold filling and microhardness of 1% Fe titanium alloys

We examined the mold filling capacity and microhardness of two industrial 1% Fe titanium alloys: Super-TIX800 (Nippon Steel Corp.) (Fe: 0.910%, O: 0.370%, N: 0.005%) and Super-TIX800N (Nippon Steel Corp.) (Fe: 0.960%, O: 0.300%, N: 0.041%). Two wedge-shaped acrylic patterns (with 30 degrees or 15 degrees angles) were prepared. Each alloy was cast in a centrifugal casting machine. Mold filling was evaluated as the missing length between the tip of the casting and the theoretical tip. Vickers hardness of the edge of the castings was also determined. For both angles tested, there were no significant differences (p>0.05) in mold filling among these alloys and the control (CP Ti). The results of testing the microhardness near the cast surfaces indicated that the hardened reaction layers on these alloys were thinner at the edge compared to CP Ti.     

Tensile bond strength of cast commercially pure titanium dowel and cores cemented with three luting agents

PurposeThe purpose of this study was to compare the tensile strength of commercially pure titanium dowels and cores cemented with zinc phosphate or resin cements.MethodsTwenty-one extracted human canines were endodontically treated. The root preparations were accomplished using Largo reamers (10 mm in depth and 1.7 mm in diameter). Acrylic resin patterns for the dowel and cores were made, and specimens were cast in commercially pure titanium (n = 7) and divided in three groups: TZ–CP Ti dowels luted with zinc phosphate luting agent, TP–CP Ti dowels luted with Panavia F and TR–CP Ti dowels luted with RelyX U100. Tensile strengths were measured in a universal testing machine at a crosshead speed of 0.5 mm/min. The results (N) were statistically analyzed by ANOVA and Tukey tests (α = 0.01).ResultsThe ANOVA indicated that there were significant differences among the groups tested. A Tukey multiple comparison procedure was performed and revealed statistically significant higher retention values for the dowel luted with RelyX U100 when compared with zinc phosphate or Panavia F.ConclusionCast commercially pure titanium dowels and cores fixed with RelyX U100 cement presented superior bond strength retention when compared to zinc phosphate and Panavia F.     

Metal-ceramic bond strength of Co-Cr alloy fabricated by selective laser melting

ObjectivesThis study was to evaluated the metal–ceramic bond strength of a Co–Cr dental alloy prepared using a selective laser melting (SLM) technique.MethodsTwo groups comprised of twenty Co–Cr metal bars each were prepared using either a SLM or traditional lost-wax casting method. Ten bars from each group were moulded into standard ISO 9693:1999 dimensions of 25 mm × 3 mm × 0.5 mm with 1.1 mm of porcelain fused onto an 8 mm × 3 mm rectangular area in the centre of each bar. Metal–ceramic bonding was assessed using a three-point bending test. Fracture mode analysis and area fraction of adherence porcelain (AFAP) were determined by measuring Si content of specimens by SEM/EDS.ResultsStudent's t-test within the groups demonstrated no significant difference for the mean bond strength between the SLM and traditional cast sample groups. While SEM/EDS analysis indicated a mixed fracture mode on the debonding interface of both the SLM and the cast groups, the SLM group showed significantly more porcelain adherence than the control group (p < 0.05).ConclusionsThe SLM metal–ceramic system exhibited a bonding strength that exceeds the requirement of ISO 9691:1999(E) and it even showed a better behaviour in porcelain adherence test comparable to traditional cast methods.     

Mold filling and dimensional accuracy of titanium castings in a spinel-based investment

ObjectivesAim of the study was to analyze the mold filling capacity and the dimensional accuracy of a spinel-based investment for titanium castings.MethodsExpansion of the investment in dependence of the preheating temperature was measured in a dilatometer. The degree of transformation of MgO and Al₂O₃ to spinel (MgAl₂O₄) was evaluated by means of X-ray powder diffraction. Mold filling capacity was assessed by casting a grid and calculating the percentage of completed segments. Dimensional accuracy was analyzed by casting a hollow cylinder and measuring the difference between the inner diameter of the resin pattern and the resulting titanium casting.ResultsSpinel formation starts at 819 °C. Diffraction patterns prove the formation of spinel from MgO and Al₂O₃. The amount of spinel increases with increasing preheating temperature. The final expansion of the investment at the end of the preheating cycle at 450 °C shows a linear correlation to the maximum preheating temperature. The degree of mold filling is reciprocal to the preheating temperature. The dimensional accuracy shows a linear correlation to the amount of spinel. Best dimensional accuracy was obtained at about 900 °C. After a preheating temperature of 884 °C, as recommended by the manufacturer, the cast specimens showed a slightly lower inner diameter as compared to the resin patterns.SignificanceThe results suggest that with the spinel investment analyzed an excellent accuracy of titanium castings may be obtained.     

Effects of steam and dry-heat sterilization on bending properties of NiTi wires

PurposeNickel–titanium arch wires have a prominent role in orthodontic appliances due to their desirable mechanical properties. The purpose of the present study is to determine the effects of autoclave and dry-heat sterilization on the bending properties of three types of NiTi superelastic wires.MethodsIn this experimental study, three commercial types (Force I, Rematitan LITE, and G &; H) of superelastic NiTi wires, 0.016 in. in diameter, were selected. From each type of wire, 20 specimens were prepared. The specimens were initially subjected to the three-point bending test at a rate of 1 mm/min on the Dartec testing machine in order to determine their load-deflection properties before sterilization. Then, 10 specimens of each type of wire were subjected to dry-heat sterilization (160 °C, 120 min) and 10 to autoclave sterilization (121 °C, 15 psi, 24 min). After sterilization, the specimens were subjected to the three-point bending test again and their load-deflection curves were plotted. The values for bending properties obtained before and after sterilization were subjected to the Duncan and ANOVA tests at the 0.05 significance level.ResultsOur findings revealed considerable changes in the load-deflection properties of the test wires as a result of dry-heat sterilization. These changes included decreasing in applied force in both loading and unloading phases and reducing of wire superelasticity.ConclusionSteam and dry-heat sterilization cause changes in the mechanical properties of superelastic NiTi arch wires.     

Laser surface treatment to improve mechanical properties of cast titanium

ObjectiveThe aim of this study was to investigate the effect of laser surface treatment on the mechanical properties of cast titanium and to compare with those of the Co–Cr alloy.MethodsDumbbell-shaped cast specimens were prepared for commercially pure titanium (grade 2) and Co–Cr alloy. The cast titanium specimens were laser-treated on the surface using a dental Nd:YAG laser machine at 240 V and 300 V. After laser treatment, tensile testing was conducted to obtain the tensile strength, percent elongation and modulus of elasticity. The hardness depth profile was made from the cast subsurface (25 μm) to 1500 μm in depth using the cross-sections of the cast rods with the same diameter as the dumbbell. The data were statistically analyzed by ANOVA/post hoc tests (p < 0.05).ResultsThe highest tensile strength was obtained for the titanium specimens laser-treated with 300 V followed by the 240 V and the control specimens. The laser-treated titanium specimens with 300 V showed a tensile strength equivalent to the Co–Cr alloy. Although the highest modulus of elasticity was found for the specimens laser-treated with 240 V, there were no significant differences in elastic modulus among 240 V, 300 V and Co–Cr. The laser-treated groups showed significantly lower hardness at the subsurface of 25 μm and maintained their hardness until the depth of 400 μm. The hardness of the control group was very high at 25 μm depth, and dramatically decreased until the 200 μm depth.ConclusionThe results of tensile testing and hardness depth-profiling indicated that the laser treatment significantly improved the mechanical properties of cast titanium by improving the surface integrity of the cast surface contamination.     

Tensile bond strength between tooth-colored porcelain and sandblasted zirconia framework

PurposeThe purpose of this study was to examine the bond strength between tooth-colored porcelain and sandblasted zirconia framework.MethodsThe surfaces of zirconia specimens that had been cut into a size suitable for a bending test were sandblasted at three different pressures (0.2, 0.4 and 0.6 MPa). The surface roughness of each specimen was measured and then a 3-point bending test was performed. After that, other zirconia specimens simulating a crown framework were fabricated and their surfaces were sandblasted. Three types of tooth-colored porcelain were fired onto the surface of those zirconia specimens, and the tensile bond strength between the two substances was examined.ResultsWhen the sandblasting pressure was increased, the surface roughness of zirconia specimens tended to become, but the flexural strength remained unchanged. The specimens simulating a zirconia framework had a higher strength of bond when sandblasted at 0.4 or 0.6 MPa than when blasted at 0.2 MPa. The zirconia specimens sandblasted at a pressure of 0.4 MPa had a bond strength to tooth-colored porcelain of 37.7–49.5 MPa.ConclusionWhen sandblasted at a pressure of 0.4 MPa, the zirconia specimens developed a strong bond with the tooth-colored porcelain, regardless of the type of porcelain.     

The effect of a ceramic coating on the cpTi–porcelain bond strength

ObjectivesTo investigate the bond strength between cpTi and low fusing porcelains after different treatments.Methods72 patterns were covered with a ceramic coating and invested with phosphate-bonded material (group A), another 72 were invested with magnesia material (group B) and all cast with cpTi. 31 solid castings were selected from each group. The castings of group B were ground and sandblasted, while the castings of group A were only sandblasted. Aluminum content of the metal surface was determined by EDS and castings were submitted to a 3-point bending test to determine the modulus of elasticity (E). The porcelains Duceratin Plus, Noritake Ti22 and Triceram were applied respectively and specimens were submitted to a 3-point bending test. The fracture mode and the remaining porcelain were determined by optical microscopy and SEM/EDS. Bond strength and fracture mode were calculated by two-way ANOVA.ResultsThe E of groups A and B was 98.3 GPa and 98.6 GPa respectively. The bond strength was 26 ± 3 MPa (Duceratin Plus), 28 ± 3 MPa (Noritake Ti22), 27 ± 2 MPa (Triceram) for group A and 24 ± 1 MPa, 29 ± 2 MPa, 27 ± 1 MPa for group B respectively. No significant differences were found for the same porcelain between the two groups (p < 0.05). A significant difference was found between Duceratin Plus and Noritake Ti22, for group B (p < 0.05). The mode of failure was mainly adhesive for all specimens. A significant reduction in aluminum was recorded in all subgroups.SignificanceThe special coating of patterns makes the Ti casting procedure inexpensive, without reducing the metal–ceramic bond strength.     

Effect of mold temperatures on interface between primary and secondary castings of cast-on method for precision metal frameworks

PurposeThe purpose of the present study was to obtain fundamental data for application of the cast-on method by evaluating the effect of mold temperatures on the interface between primary and secondary castings in detail.MethodsSilver–palladium–gold alloy (Ag–Pd–Au), type-4 gold alloy (Type4), and chromium–cobalt alloy (Cr–Co) were used in the present study. A polished flat, square metal plate, 10.0 mm × 10.0 mm × 1.0 mm, was used as the primary casting. A wax pattern, 2.0 mm in diameter and 2.0 mm thick, was prepared for the secondary casting and invested together with the primary casting. The mold was heated at 600, 700 and 800 °C for Ag–Pd–Au and Type4, and 700, 800 and 900 °C for Cr–Co. After casting, the mold was embedded and sectioned. The cross-section was observed using a scanning electron microscope (SEM) and analyzed using energy dispersive X-ray spectroscopy (EDS). The gaps between the primary and secondary castings were analyzed for each alloy by analysis of variance and Tukey's honestly significant difference test. The significance level was set at 0.05. The heated primary casting without the secondary casting was examined using a thin film X-ray diffractometer (XRD).ResultsGaps were observed between the primary and secondary castings in all examined conditions. The primary casting surface was covered with oxide layers such as CuO and Cr₂O₃, and became rough with an increase of the mold temperature.ConclusionsThe results suggested that the cast-on method was influenced by the mold temperature.     

Effect of surface roughness and thermal cycling on bond strength of C.P. titanium and Ti-6Al-4V alloy to ceramic

PurposeStudying the effect of surface roughness and thermal cycling on titanium–ceramic bonding.MethodsOne hundred fourteen samples in the form of bar for the C.P. titanium and Ti–6Al–4V alloy were used. They were divided into two groups according to the type of bar. Each group was then subdivided according to the type of surface treatment to three subgroups, control, airborne-particle abrasion and silica coated. Each subgroup was subdivided into two classes according to the type of test (surface roughness and bond strength). Samples used for the bond strength test were veneered. These samples were subdivided into two subclasses according to thermal cycling; whether without thermal cycling or after 6000 thermal cycles.ResultsThe surface roughness test results showed that silica coating recorded the highest surface roughness. Also C.P. titanium gave higher value of surface roughness than Ti–6Al–4V alloy. As regard the bond strength, the airborne-particle abrasion classes and the silica coated classes recorded bond strength values above the acceptable limit of 25 MPa determined in ISO 9693. As regard thermal cycling, the results showed that aging by thermal cycling decreased the metal–ceramic bond strength.ConclusionsThe airborne-particle abrasion and the silica coating are acceptable treatments for titanium–ceramic restorations. Increasing surface roughness of C.P. titanium and Ti–6Al–4V alloy not necessarily results in an increase in their bond strength to ceramics. Aging affects the metal–ceramic bond strength.     

Titanium clasp fabricated by selective laser melting,CNC milling,and conventional casting: a comparative in vitro study

Purpose

This study aimed to investigate the effects of selective laser melting (SLM), milling methods, and casting on the behavior of titanium clasp.

Effect of thermal expansion mismatch on the Y-TZP/veneer interfacial adhesion determined by strain energy release rate

PurposesThe aim of this study was to assess the effect of differences in the thermal expansion behaviour of veneering ceramics on the adhesion to Y-TZP, using a fracture mechanics approach.MethodsSeven veneering ceramics (VM7, VM9, VM13, Lava Ceram, Zirox, Triceram, Allux) and one Y-TZP ceramic were investigated. Thermal expansion coefficients and glass transition temperatures were determined to calculate residual stresses (σ_R, MPa) between core and veneer. Subsequently, the veneering ceramics were fired onto rectangular shaped zirconia specimens, ground flat and notched on the veneering porcelain side. Then specimens were loaded in a four-point bending test and load-displacement curves were recorded. The critical load to induce stable crack extension at the adhesion interface was evaluated to calculate the strain energy release rate (G, J/m²) for each system.ResultsResidual stresses ranged from ?48.3 ± 1.5 MPa (VM7) to 36.1 ± 4.8 MPa (VM13) with significant differences between all groups (p < 0.05). The strain energy release rate of the Y-TZP/veneer specimens ranged from 8.2 ± 1.7 J/m² (Lava Ceram) to 17.1 ± 2.8 J/m² (VM9). Values for G could not be obtained with the VM7, Allux and VM13 specimens, due to spontaneous debonding or unstable crack growth. Except for Triceram and Zirox specimens, strain energy release rate was significantly different between all groups (p < 0.05).ConclusionThermal residual stresses and strain energy release rates were correlated. Slight compressive stresses in the region of ?20 MPa were beneficial for the Y-TZP/veneer interfacial adhesion. Stresses higher or lower than this value exhibited decreased adhesion.     

Effect of time on the post-irradiation curing of six resin-based composites

ObjectivesTo evaluate the effect of time on the Vickers microhardness (VH) at the top and bottom surfaces of six conventional resin-based composites (RBCs) up to twelve weeks after light curing.MethodsFive specimens of Filtek Supreme Ultra, Herculite Ultra, Mosaic Ultra, Tetric EvoCeram, TPH Spectra HV, and Venus Pearl were packed into opaque molds that were 2.3 mm in diameter and 2.5 mm deep. The uncured RBC specimens were covered by a polyester strip and photo-cured with an Elipar DeepCure-S light-curing unit (LCU) according to the manufacturer's instructions. After irradiation, the polyester strip was removed, and the Vickers microhardness was measured immediately at top and bottom surfaces. The hardness measurements were repeated after 30 min, 1 h, 2 h, 4 h, 24 h, 1 week, 4 weeks, and 12 weeks. In between, the specimens were stored in dry and dark conditions at 37 °C. Two-way ANOVA (α = 0.05) followed by Tukey–Kramer post hoc multiple comparison tests were used to determine where statistically significant differences existed.ResultsThe micro-hardness values at the top surface always exceeded those at the bottom surface. A significant logarithmic increase of the micro-hardness due to post-irradiation curing took place between 30 min and 24 h (p < 0.05). There was no significant increase in the VH after 24 h. Depending on the RBC, compared to the immediate values the hardness 24 h post-irradiation had increased by 11–27% at the top surface and by 21–58% at the bottom.SignificanceEven after 12 weeks, the bottom hardness values never reached the top microhardness values. The results of studies that wait 24 h or longer before measuring the properties of RBC specimens will be significantly enhanced by the impact of post-irradiation curing. Especially within the first 4 h, the time when specimens are measured is critical information and should be reported.     

The influence of mold temperature on the fit of cast crowns with commercially pure titanium

Commercially pure titanium (CP Ti) has been widely applied to fabricate cast devices because of its favorable properties. However, the mold temperature recommended for the manufacture of casts has been considered relatively low, causing inadequate castability and poor marginal fit of cast crowns. This study evaluated and compared the influence of mold temperature (430 degrees C--as control, 550 degrees C, 670 degrees C) on the marginal discrepancies of cast CP Ti crowns. Eight bovine teeth were prepared on a mechanical grinding device and impressions were used to duplicate each tooth and produce eight master dies. Twenty-four crowns were fabricated using CP Ti in three different groups of mold temperature (n = 8): 430 degrees C (as control), 550 degrees C and 670 degrees C. The gap between the crown and the bovine tooth was measured at 50 X magnification with a traveling microscope. The marginal fit values of the cast CP Ti crowns were submitted to the Kruskal-Wallis test (p = 0.03). The 550 degrees C group (95.0 microm) showed significantly better marginal fit than the crowns of the 430 degrees C group (203.4 microm) and 670 degrees C group (213.8 microm). Better marginal fit for cast CP Ti crowns was observed with the mold temperature of 550 degrees C, differing from the 430 degrees C recommended by the manufacturer.     

INFLUENCE OF THE FINAL TEMPERATURE OF INVESTMENT HEALTING ON THE TENSILE STRENGTH AND VICKERS HARDNESS OF CP TI AND TI-6AL-4V ALLOY

The aim of the work was to evaluate the influence of the temperature of investment healting on the tensile strength and Vickers hardness of CP Ti and Ti-6Al-4V alloy casting. Were obtained for the tensile strength test dumbbell rods that were invested in the Rematitan Plus investment and casting in the Discovery machine cast. Thirty specimens were obtained, fiftten to the CP Titanium and fifteen to the Ti-6Al-4V alloy, five samples to each an of the three temperatures of investment: 430°C (control group), 480°C and 530°C. The tensile test was measured by means of a universal testing machine, MTS model 810, at a strain of 1.0 mm/min. After the tensile strenght test the specimens were secctioned, embedded and polished to hardness measurements, using a Vickers tester, Micromet 2100. The means values to tensile tests to the temperatures 430°C, 480 and 530: CP Ti (486.1 – 501.16 – 498.14 –mean 495.30 MPa) and Ti-6Al-4V alloy (961.33 – 958.26 – 1005.80 – mean 975.13 MPa) while for the Vickers hardness the values were (198.06, 197.85, 202.58 – mean 199.50) and (352.95, 339.36, 344.76 – mean 345.69), respectively. The values were submitted to Analysis of Variance (ANOVA) and Tukey^,s Test that indicate differences significant only between the materials, but not between the temperature, for both the materias. It was conclued that increase of the temperature of investment its not chance the tensile strength and the Vickers hardness of the CP Titanium and Ti-6Al-4V alloy.     

Fatigue resistance and retentive force of cast clasps treated by shot peening

PurposeThe fatigue failure of denture clasps has often been observed in removable partial denture rehabilitation. To increase their fatigue strength, shot peening was evaluated as a surface treatment. In this study, we evaluated the fatigue resistance and retention of cast clasps by using a shot peening treatment.MethodsA cobalt–chromium (Co–Cr) alloy, commercial pure titanium (CP Ti), silver–palladium–gold (Ag–Pd–Au), and a gold–platinum (Au–Pt) alloy were cast and then treated with shot peening. The retentive forces of the clasps were measured up to a repetition of 10,000 insertion/removal cycles in distilled water at 37 °C. A fatigue test was also performed using a 15-mm cantilever. Specimens were loaded with a constant deflection of 2.0 mm with 20 Hz. A shot peening treatment indicated a better stability of retentive forces than that without shot peening. The retentive force of Co–Cr clasps without shot peening was remarkably decreased at 500 cycles of insertion/removal repetition.ResultsThe clasps with a shot peening treatment provided approximately 1.4–3.6 times higher fatigue strengths than those without a shot peening treatment.ConclusionTo prevent the fatigue failure of the denture clasps and use the dentures for long term, a shot peening treatment would be recommended.     

New insight into the "depth of cure" of dimethacrylate-based dental composites

ObjectivesTo demonstrate that determination of the depth of cure of resin-based composites needs to take into account the depth at which the transition between glassy and rubbery states of the resin matrix occurs.MethodsA commercially available nano-hybrid composite (Grandio) in a thick layer was light cured from one side for 10 or 40 s. Samples were analyzed by Vickers indentation, Raman spectroscopy, atomic force microscopy, electron paramagnetic imaging and differential scanning calorimetry to measure the evolution of the following properties with depth: microhardness, degree of conversion, elastic modulus of the resin matrix, trapped free radical concentration and glass transition temperature. These measurements were compared to the composite thickness remaining after scraping off the uncured, soft composite.ResultsThere was a progressive decrease in the degree of conversion and microhardness with depth as both properties still exhibited 80% of their upper surface values at 4 and 3.8 mm, respectively, for 10 s samples, and 5.6 and 4.8 mm, respectively, for 40 s samples. In contrast, there was a rapid decrease in elastic modulus at around 2.4 mm for the 10 s samples and 3.0 mm for the 40 s samples. A similar decrease was observed for concentrations of propagating radicals at 2 mm, but not for concentrations of allylic radicals, which decreased progressively. Whereas the upper composite layers presented a glass transition temperature – for 10 s, 55 °C (±4) at 1 mm, 56.3 °C (±2.3) at 2 mm; for 40 s, 62.3 °C (±0.6) at 1 mm, 62 °C (±1) at 2 mm, 62 °C (±1.7) at 3 mm – the deeper layers did not display any glass transition. The thickness remaining after scraping off the soft composite was 7.01 (±0.07 mm) for 10 s samples and 9.48 (±0.22 mm) for 40 s samples.SignificanceAppropriate methods show that the organic matrix of resin-based composite shifts from a glassy to a gel state at a certain depth. Hence, we propose a new definition for the “depth of cure” as the depth at which the resin matrix switches from a glassy to a rubbery state. Properties currently used to evaluate depth of cure (microhardness, degree of conversion or scraping methods) fail to detect this transition, which results in overestimation of the depth of cure.     

In vitro study of the effects of fluoride-releasing dental materials on remineralization in an enamel erosion model

ObjectivesThis study was conducted to compare the remineralization effects of five regimens on the loss of fluorescence intensity, surface microhardness, roughness and microstructure of bovine enamel after remineralization. We hope that these results can provide some basis for the clinical application of these materials.MethodsOne hundred bovine incisors were prepared and divided into the following five groups, which were treated with distinct dental materials: (1) Clinpro? XT varnish (CV), (2) F-varnish (FV), (3) Tooth Mousse (TM), (4) Fuji III LC^® light-cured glass ionomer pit and fissure sealant (FJ) and (5) Base Cement^® glass polyalkenoate cement (BC). Subsequently, they were detected using four different methods: quantitative light-induced fluorescence, microhardness, surface 3D topography and scanning electron microscopy (SEM).ResultsThe loss of fluorescence intensity of CV, BC and FJ groups showed significant decreases after remineralization (p < 0.05). The microhardness values of the BC group were significantly higher than those of the other groups (p < 0.05) after 6 weeks of remineralization. The CV group's surface roughness was significantly lower than those of the other groups after 6 weeks of remineralization (p < 0.05). Regarding microstructure values, the FV group showed many round particles deposited in the bovine enamel after remineralization. However, the other four groups mainly showed needle-like crystals.ConclusionsGlass ionomer cement (GIC)-based dental materials can promote more remineralization of the artificial enamel lesions than can NaF-based dental materials. Resin-modified GIC materials (e.g., CV and FJ) have the potential for more controlled and sustained release of remineralized agents. The effect of TM requires further study.     

Biological behavior of fibroblast-like cells cultured on anodized-hydrothermally treated titanium with a nanotopographic surface structure

PurposeThe interface between the transmucosal portion of endosseous implants surface and the connective tissue is characterized by fibroblast-rich barrier tissue, which is important for the long-term stability and maintenance of the implant. This study investigated the effect of cell adhesion on focal adhesion kinase (FAK) protein and on gene expression over a 72-h culture period. Fibroblast-like cells were cultured on anodized-hydrothermally treated commercially pure titanium with nanotopographic structure (SA-treated c.p.Ti) surfaces.MethodsMurine fibroblast-like NIH/3T3 cells were cultured for 10–72 h on c.p.Ti, anodic oxide (AO) c.p.Ti, and SA-treated c.p.Ti disks. Cell morphology was analyzed using scanning electron microscopy (SEM). Cytoskeletal structure and FAK protein localization were analyzed using confocal laser scanning microscopy (CLSM). FAK mRNA levels were analyzed using real-time quantitative RT-PCR.ResultsSEM and CLSM showed increased NIH/3T3 cell adhesion with time, and actin filaments oriented parallel with the filopodium-like extensions on all disks. Filopodium-like extensions were bound tightly to the nanotopographic structure surface of cultures on SA-treated c.p.Ti, and especially at 72 h. FAK protein was localized along cellular extensions on SA-treated c.p.Ti and the expression of FAK mRNA was significantly higher on these disks than on c.p.Ti and AO c.p.Ti after 72 h (P < 0.05).ConclusionsNIH/3T3 fibroblast-like cells have the capacity to adhere to SA-treated c.p.Ti as a transmucosal portion of implant surface material and express focal adhesion molecules, which may play a key role in the maintenance of a mucosal tissue barrier